B14 - Variation And Evolution Flashcards
(32 cards)
What is variation?
Variation is the differences in the characteristics of individuals in a population
Variation may be due to differences in inherited genes (genetic causes), the conditions in which organisms develop (environmental causes) or a combination of both
• in sexually reproducing populations there are many different combinations of alleles. This means that genetic variation is high
Nature - genetic variation
• basic characteristics are a result of genes inherited from our parents
• eye colour, nose shape, dimples
Nurture - environmental variation
• conditions in which it develops
• genetically identical plants can be grown under different conditions or with different mineral ions, and the resulting plants do not look identical
• plants deprived of light, CO2 or mineral ions do not make as much food as plants with everything
How can mutations lead to human evolution?
• most mutations do not affect the phenotype if a mutation creates a new phenotype that is better adapted to environmental changes, the mutation is likely to spread throughout the population over generations
Evolution and speciation
• Evolution is the gradual change of inherited characteristics of biological populations over time
• speciation happens when two animal populations diverge a lot
Why does speciation happen?
• result of evolution
• natural mutations can create new alleles and two populations can begin to diverge
What is speciation?
• when the average phenotypes of two populations have diverged so much that the two populations can no longer breed to produce fertile offspring
• two different species have been formed
Evolution
• discovery of genes is crucial to understanding - provides clear mechanism by which traits are inherited and varied within populations
• resistance results from random genetic mutations favoured by natural selection
Natural selection
• proposed by Charles Darwin in 1859
•‘genetic variation, survival of the fittest (individuals possessing genes that make them better adapted to the environment will have a greater chance of survival), breeding, best characteristics survive
Selective Breeding
• when humans choose animals and crops to breed, based on their genetic characteristics
• promotes genetic characteristics seen as desirable
Steps for selective breeding
• choose parents who most strongly display the desired characteristic
• breed chosen parents
• from the resultant offspring, choose their offspring that best display the desired characteristic
• breed these chosen offspring
• repeat this process of breeding and reselection over many generations, until all the offspring show the desired characteristics
• it is artificial selection
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Examples of selective breeding
• disease resistance in crops is a useful characteristic because it improves yield
• gentle natured domestic dogs
• crops, dogs, flowers, farm animals
• yield = food production
Dangers of selective breeding
• reduced variation - makes it harder for species to adopt to environmental changes
• inbreeding - some breeds become particularly susceptible to disease or inherited defects (reproduction of animals that are related to each other)
• e.g. French bulldogs have breathing problems due to flat faces
What is a peat bog?
• semi-decomposed plant matter often used for fuels.
• preservation of matter due to limited oxygen to the matter as they have been water logged
• when oxygen is removed, bacteria is no longer able to respire therefore reducing the rate of decomposition
• bodies found preserved because there is a lack of microorganism breaking it down
• Destroying them means more CO2 is released if peat is burnt or from microbial respiration during decomposition.
• habitat destruction
Why is deforestation a problem?
• tropical rainforests contain the most biodiversity on the planet. When we lose these forests, we reduce biodiversity and species become extinct, which could have contributed to medicine and food resources for the future
How does deforestation increase the amount of CO2?
• burning trees = combustion = release of CO2
• dead vegetation after decomposes and the microorganisms use up oxygen and release more CO2 as they respire
• reduces the rate at which CO2 is removed because there is less photosynthesis - lose vital carbon dioxide ‘sink’
Why are the number of peat bogs and peatlands decreasing?
• massive carbon store - therefore they are burnt and destroyed for fuel and used as garden compost
• this is a cause for concern because the organism that depend on peat bogs are destroyed, therefore more loss of biodiversity
Gardeners using peat
• peat is widely used by gardeners to improve the properties of the soil and provide an ideal environment for seed germination, which helps to increase food production
• however when peat is used in gardens CO2 is released into the atmosphere and the carbon store is lost - biodiversity loss
• UK government wants gardeners to use ‘peat-free’ composts
• this will reduce CO2 emissions and conserve peat bogs/peat lands as habitats for biodiversity
• compost can be made from bark, garden waste, coconut husks - problem is persuading gardeners to use them
Government action against gardeners using peat
• want gardeners to use peat free compost
• this will reduce CO2 emissions and conserve peat bogs/peatlands as habitats for biodiversity
• compost can be made from bark, garden waste, coconut husks - problem is persuading gardeners to use them
Carbon sinks
• forests - absorb CO2 via photosynthesis
• oceans - CO2 dissolves in water and phytoplankton use carbon for their skeleton and shells
• peat bogs - lock away CO2, when burnt - CO2 released back into the atmosphere
The theory of evolution
Discovered by Charles Darwin - 1859 book
The theory of evolution by natural selection states that all species of living things have evolved from simple life forms that first developed over 3 billion years ago.
• Mutations occur continuously. Very rarely a mutation leads to a new phenotype. If the new phenotype is suited to an environmental change it can lead to a relatively rapid change in the species.
What is genetic engineering?
Genetic engineering involves modifying (changing) the genetic material of an organism. The gene for a desirable characteristic is cut out of one organism and transferred to the genetic material in the cells of another organism. This gives the genetically engineered organism a new, desirable characteristic. For example, plant crops have been genetically engineered to be resistant to certain diseases, or to produce bigger, better fruits.
Process of genetic engineering
Enzymes are used to isolate and ‘cut out’ the required gene from an organism, for example, a person.
• The gene is then inserted into a vector using more enzymes. The vector is usually a bacterial plasmid or a virus.
• The vector is then used to insert the gene into the required cells, which may be bacteria, animal, fungi, or plants
• Genes are transferred to the cells at an early stage of their development (in animals, the egg, or very early embryo). As the organism grows, it develops with the new desired characteristics from the other organism. In plants, the desired genes are often inserted into meristem cells which are then used to produce identical clones of the genetically modified plant.
Example of genetic engineering with bacteria
The human insulin gene can be inserted into bacteria to produce human insulin:
1. The insulin gene is first cut out of human DNA using enzymes.
2. The same enzymes are then used to cut the bacterial DNA and different enzymes are used to insert the human insulin gene.
3. The bacteria are then allowed to multiply. The insulin they produce while they grow is purified and used by people with diabetes.
